Field of the Invention
The present invention relates to an art of a heat pipe having a wick structure.
Discussion of the Related Art
Heat pipes have been widely used as a heat transport device. The conventional heat pipe comprises a tubular sealed container and working fluid encapsulated therein, and brought into contact to a heat generating member. The working fluid is vaporized by a heat of the heat generating element transmitted to one end of the heat pipe and aspirated to the other end side due to difference in pressure inside and outside.
The end portion of the heat pipe thus brought into contact to the heat generating element serves as an evaporating portion where evaporation of the working fluid takes place, and the other end portion is brought into contact to a radiation member to serve as a condensing portion where condensation of the working fluid takes place as a result of transmitting heat to the radiation member. The working fluid condensed at the condensing portion is returned to the evaporating portion by a capillary pumping of a wick structure arranged in the heat pipe.
The container of the heat pipe may be altered arbitrarily according to a configuration of a cooling object. For example, if the cooling object is a small electronic device, the container of the heat pipe may be flattened to be fitted into the device.
JP-A-2013-002641 describes a flat heat pipe having a wick structure. According to the teachings of JP-A-2013-002641, a bundle of thin metal fibers is used as the wick.
However, the wick structure taught by JP-A-2013-002641 occupies an inner space of the container serving as a vapor passage. In the flat heat pipe of JP-A-2013-002641, the inner space of the container is rather narrow and hence divided into two spaces by the wick formed throughout between upper and lower inner faces. In the heat pipe of this kind, the vapor is not allowed to flow through the vapor passages in sufficient amount.
Nonetheless, if number of fibers forming the wick is reduced to expand the vapor passage in the heat pipe taught by JP-A-2013-002641, the capillary pumping of the wick may be weakened and hence the working fluid cannot be returned sufficiently to the evaporating portion.
In addition, it is difficult to arrange a wick structure having a complicated structure in the thin flat sealed container and there is a need for simplifying manufacturing of the heat pipes.